Remediation of eutrophic freshwater systems using phosphorus fixing chemicals.

Applications are invited for a funded PhD studentship tenable in the Environmental Sciences Research Institute at the Coleraine Campus.

Supervisors: Dr Richard Douglas & Dr Sally Cook
Contact Details: [Email Address Removed]

It has been estimated in the US that freshwater eutrophication can cost up to £1.7 billion per year in damage costs (Dodds et al., 2009), while in the UK, the cost has been put at £114 million per year ar (Pretty et al., 2003). The greatest proportion of these economic losses can be attributed to drinking water treatment costs, lakefront property values, cleanup costs to waterways to maintain flood defence and preserve channel capacity and reduced recreational and amenity value of water bodies for water sports, angling, and general amenities.

Due to improved management practice, the external nutrient loading has generally decreased to lakes during recent decades, however, many shallow eutrophic lakes still have difficulties in improving their ecological condition (Egemose et al., 2010). This lack of improvement is often caused by the release of years of accumulated nutrients (phosphorus) from the lake sediment into the water column during the spring and summer months. The increased bioavailable phosphorus then supports phytoplankton growth which can result in extreme ecological change for the aquatic system. Implied recovery times after cessation of nutrient inputs varies widely, but recent work has modelled recovery times of upwards to a century (McCrackin et al., 2017).

The addition of phosphorus fixing chemicals have been used to improve lakes ecological condition and reverse eutrophication. This eutrophication management strategy is both expensive and the longterm success is uncertain, however, the results can be almost instantaneous. Knowledge of the effects of lake resuspension processes and sediment stabilization on phosphorus fixing chemicals is limited. This project will work alongside a recently awarded INTERREG CatchmentCARE €13.7 million grant and use sediment trapping techniques and a remote access sampler to explore the behaviour and stability of sediments before and after a phosphorus fixing chemical has been added to a range of lakes. The student will be trained in chemical techniques, GIS, boat handling and will use high resolution sampling equipment (e.g. Technicap sediment trap, Mclane Remote Access sampler and YSI Multiparameter Sondes) to investigate related sedimentation processes in lakes from border catchments in the North and South of Ireland. The output of this project will improve the phosphorus fixing regime recommended for lakes dependent on basic knowledge of a lake’s sedimentation processes. This will result in the targeted and successful application of phosphorus fixing chemicals to problem lakes on a larger scale, improving both the trophic status and the economic impact.